1. Field of the Invention
The invention pertains to the processing of signals coming from the matrix structures of light-sensitive detectors, especially infrared sensors and, more especially, to a device that uses charge transfer devices for the analog multiplexing of signals from detectors of this type.
2. Description of the Prior Art
Several prior art methods use charge transfer registers to multiplex samples of analog signals. In one such method, samples of analog signals from several inputs (n inputs) are transferred in parallel to the various stages of an output charge transfer register and are read serially at the analog output of this output register. The transfer frequency of the output register is n times the frequency of the input samples.
In another method, the samples coming from n input registers are introduced into an output register by successive commands, distributed over one cycle of the input signal, from n analog gates connecting the outputs of these registers to the input of the output register.
In the two multiplexing modes briefly described above, the transfer of analog samples between the input registers and the output register is done by transferring analog charges. These methods require a juxtaposition between the input register outputs and the input or inputs of the output register. Consequently, the size of the output register, namely its length when the inputs are in parallel at the stages of an output register, or its width when the inputs are connected to the input of the output register through analog gates, is made necessary by the repetition pitch of the input registers. Now, these dimensions which are made necessary may be incompatible with the geometry required for efficient transfer in the output register, or they may be excessive with respect to the charge to be transferred, the result of this being an unnecessary increase of unwanted dark current in the output charge transfer register.
Furthermore, these two modes of multiplexing require control signals:
A single control signal for the first transfer mode: this does not constitute much of a constraint;
As many control signals as there are gates in the second method, resulting in a more complicated and, therefore, less reliable system.